use double, not single quote

configure

@@ -15,7 +15,7 @@
 # NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 # WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-# From configure.in Revision: 1.172 
+# From configure.in Revision: 1.173 
 
 ## libtool.m4 - Configure libtool for the target system. -*-Shell-script-*-
 ## Copyright (C) 1996-1999 Free Software Foundation, Inc.
@@ -1204,7 +1204,7 @@ if test "X$openssl" = "X" ; then
 else
     DST_PRIVATEOPENSSL=''
     dst_privateopenssl=''
-    DST_OPENSSL_INC='-I$openssl/include'
+    DST_OPENSSL_INC="-I$openssl/include"
     DNS_OPENSSL_LIBS="-L$openssl/lib -lssl -lcrypto"
     DST_OPENSSL_LIB=''
     echo "$ac_t""using openssl from $openssl/lib and $openssl/include" 1>&6

configure.in

@@ -18,7 +18,7 @@ AC_DIVERT_PUSH(AC_DIVERSION_NOTICE)dnl
 esyscmd([sed "s/^/# /" COPYRIGHT])dnl
 AC_DIVERT_POP()dnl
 
-AC_REVISION($Revision: 1.172 $)
+AC_REVISION($Revision: 1.173 $)
 
 AC_INIT(lib/dns/name.c)
 AC_PREREQ(2.13)
@@ -201,7 +201,7 @@ if test "X$openssl" = "X" ; then
 else
     DST_PRIVATEOPENSSL=''
     dst_privateopenssl=''
-    DST_OPENSSL_INC='-I$openssl/include'
+    DST_OPENSSL_INC="-I$openssl/include"
     DNS_OPENSSL_LIBS="-L$openssl/lib -lssl -lcrypto"
     DST_OPENSSL_LIB=''
     AC_MSG_RESULT(using openssl from $openssl/lib and $openssl/include)